Implementation of the AASHTO Mechanistic-Empirical Pavement Design Guide for Colorado

Abstract

The objective of this project was to integrate the American Association of State Highway and Transportation Officials (AASHTO) Mechanistic-Empirical Pavement Design Guide, Interim Edition: A Manual of Practice and its accompanying software into the daily pavement design, evaluation, rehabilitation, management, and forensic analysis practices and operations of the Colorado Department of Transportation (CDOT). The Pavement ME Design software (formerly DARWin-ME) is a state-of-the-practice analysis tool for evaluating new, reconstructed, and rehabilitated flexible, rigid, and semi-rigid pavement structures based on mechanistic-empirical principles. Using project specific traffic, climate, and materials data, Pavement ME Design estimates and accumulates pavement damage and other forms of deterioration over a specified design/analysis period and then applied transfer functions to transform damage/deterioration into distress and smoothness. The pavement designer then determines the adequacy of a desired pavement section by evaluating predicted distress and smoothness at a given reliability level at the end of the design period. As a forensic analysis tool, Pavement ME Design can be used to model a pavement structure, simulate the combined effect of application of traffic load and climate cycles, and determine the performance (or lack of) for a specified time period. The implementation of Pavement ME Design as a CDOT standard required modifications in some aspects of CDOT pavement design practices (materials testing, testing equipment, traffic data reporting, software/database integration, development of statewide defaults for key inputs, policy regarding design output interpretation, and others). Also, implementation required validation (and sometimes calibration) of the software’s “global” pavement distress and smoothness prediction models for Colorado conditions. This was accomplished using data from Long Term Pavement Performance (LTPP) projects located in Colorado and CDOT pavement management system sections. Default key data inputs were also developed, as was guidance for using the Pavement ME Design procedure for pavement design in Colorado.